The present invention relates to a new and improved construction of an automatic trackless self-propelled carriage conveyance installation or means.
In its more specific aspects, the present invention relates to a new and improved construction of an automatic trackless self-propelled carriage conveyance installation or means containing a self-propelled carriage defining a vehicle. and which carriage moves along a predeterminate path of travel or course. The carriage possesses a steered front wheel lying in the central or median lengthwise axis of the vehicle and also two rear wheels.
Automatic trackless carriage conveyance means of the previously mentioned type are known in various constructions, as for example, from the U.S. Pat. No. 3,245,493, granted Apr. 12, 1966. With that prior art design of automatic trackless carriage conveyance means, the steered front wheel of the carriage is equipped with a drive. Such prior art construction of carriage can normally only travel in forward direction on account of its steering geometry, i.e. the controlled drive wheel must be located in the front in the direction of travel of the carriage. With a reversal of the carriage travel direction, i.e. when the driven front wheel is pushing or propelling the carriage of the vehicle, uncontrollable vehicle movements tend to arise, especially when the carriage moves through or negotiates tight or narrow curves. Also, in the case of tight or small radii of curvature of the curves and in narrow aisles or corridors or the like, a simple steering of the front wheel does not suffice in order to guide the carriage precisely enough along the intended path of travel or course.
On the other hand, it is known from U.S. Pat. No. 3,628,624, granted Dec. 21, 1971, to equip a self-propelled trackless carriage with two individually driven wheels and with pivotable or swivelable travelling wheels. By differently driving the driven wheels, there can be then accomplished a steering of the carriage. This type of steering is very complicated and expensive since two independent drives or drive means and a complicated control device are needed, and even then, there is still not attained the desired successful operation since the carriage easily tends to carry-out undesired weaving or rolling motions.